| 摘要 |
PURPOSE:To make it possible to easily perform the image observation of a school of fish even if the number of receiving beams increase, by providing a color signal converter circuit and an image synthesizer circuit and displaying a received image on the same image display surface by a different color at every receiving beam. CONSTITUTION:A color signal converter circuit 17 consisting of color signal generators 18, 19, 20, an image synthesizer circuit 21 consisting of red, green and blue color signal synthesizers 22, 23, 24 and a color image display device are provided. When receiving signals S1, S2, Sn corresponding to receiving beams are inputted to the color converter circuit 17, the color signal generators 18, 19, 20 respectively change corresponding to the intensities of receiving signal S1, S2, Sn while the intensity ratio of electric signals corresponding to predeter mined red, green and blue is held and the signals corresponding tothe colors are synthesized by red, green and blue signal syntherizers 22, 23, 24 to be input ted to each color input terminal of a color image display device 25. By this method, a received image is displayed on the same display surface by a different color at every receiving beam and the state of a school of fish can be easily grasped.
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